1. Field of the Invention
The present invention relates to a stabilized insecticidal composition, and more particularly it relates to a stabilized composition of chrysanthemum-monocarboxylic acid 5-propargyl-2-furyl methyl ester (hereinafter, designated "Insecticide I"), chrysanthemum-monocarboxylic acid 2-methyl-5-propargyl-3-furyl methyl ester (hereinafter, designated "Insecticide II"), chrysanthemum-monocarboxylic acid 5-propargyl-.alpha.-ethynyl-2-furyl methyl ester (hereinafter, designated "Insecticide III"), chrysanthemum-monocarboxylic acid 5-benzyl-3-furyl methyl ester (hereinafter, designated "Insecticide IV"), or 2,2-dimethyl-3-(2,2-dichlorovinyl)cyclopropane-1-carboxylic acid 5-benzyl-3-furyl methyl ester (hereinafter, designated "Insecticide V"), each of which is known as a synthetic pyrethroid insecticide.
2. Description of the Prior Art
The above-described synthetic pyrethroid insecticides have a strong quick insecticidal activity and high safety to humans and animals, and thus they are useful as an effective insecticidal component for aerosols, oils, mosquito sticks or coils (mosquitocides), etc., in mainly domestic and epidemic prevention uses.
However, these insecticides have poor chemical stability, that is, they have the disadvantages that it is difficult to maintain their purity directly after their preparation for a specific period of time as well as after the operations necessary for producing usable insecticidal compositions containing these compounds as an active ingredient, such as, for example, mixing with water, various organic solvents, animal powders, plant powders, or mineral powders and heating. They are easily decomposed by the action of light, air, etc., with their activity being diminished and coloration occurring.
It is known and generally practiced to add 2,6-di-t-butyl-4-methylphenol (hereinafter, designated Additive C), 2-t-butyl-4-methoxyphenol (hereinafter, designated Additive D), etc., to the above-described insecticide to stabilize the insecticide but as will be shown hereinafter in the examples of this invention, the effect of such conventional additives is not always sufficient nor is the purpose for use satisfied as the case may be.